It is known that lithium-containing mood stabilizers are effective in medical treatment of manic-depressive illness, epilepsy and bipolar disorder, so that they are used widely. However, it is necessary to control or limit the concentration of lithium in a patient blood sample within a limited proper range when they are administrated to patients.
Generally, a lithium carbonate tablet (oral administration) is prescribed as mood stabilizer together with other therapeutic drug for bipolar disorder (manic-depressive insanity) or the antidepressant. The lithium carbonate (Li2CO3), however, has such a characteristic that its administration effect is exhibited only when the concentration of lithium in blood arrives at nearly a “lithium poisoning level”. In other words, when the drug is administrated, the therapeutic drug monitoring (TDM) is indispensable so as to monitor the lithium concentration in blood, since a therapeutic range is very near to the poison level.
In practice, it is necessary to control or limit the concentration of lithium in a patient blood sample within a limited range of from 0.6 to 1.2 mEq/L. In fact, when the lithium concentration in serum is lower than 0.6 mEq/L, no anti-depressive effect is expected. On the contrary, excess administration over 1.5 mEq/L of the lithium concentration in plasma will result in the lithium poisoning. Overdose result in a fatal cause of symptoms of poisoning including tremor, alalia, nystagmus, renal disturbance and convulsion. Therefore, when a sign of latently dangerous symptoms of lithium-poisoning is observed, the treatment with such lithium-containing drug must be stopped and the concentration in plasma must be re-measured so as to take a necessary measurement and to ease the lithium-poisoning.
Thus, the lithium salt is an effective medicine in the treatment of patients suffering depression, bipolar disorder, epilepsy or the like, but overdose result in serious troubles. Therefore, when a lithium-containing anti-depressive drug is administered, it is indispensable to monitor the concentration of lithium in serum and to assure that the concentration is always kept with a limited range of from 0.6 to 1.2 mEq/L.
Therefore, it was requested to determine the concentration of lithium in serum quantitatively and several liquid reagent compositions that permit colorimetric determination of lithium for the clinical laboratory test have been developed.
Patent Document 1 discloses a reagent composition used to measure the concentration of lithium in a biological sample by using cryptideinofa.
Patent Document 2 discloses an analytical reagent which reacts with lithium ion, comprising a macrocyclic compound having a pyrrole ring and eight bromine (Br) atoms combined at β position of the pyrrole ring.
Non-Patent Document 1 discloses that lithium ion can be detected by a compound in which all hydrogen bonded to carbons of tetraphenylporphyrin are replaced by fluorine.